When Mike Soldano designed the SLO-100 in 1987 he had no idea that it would transform the guitar amplifier industry, becoming one of the most iconic amps of all time. As we all know now, the SLO became a big hit, particularly in the heavy metal community, backing bands like Dokken, Ratt, and Dio. At Wacken Open Air it is perhaps the ultimate rig-of-death.
This book examines a circa 1996 version of the SLO-100 with an effects loop.
The preamp's cascading-gain architecture requires several triodes to implement, but each is dedicated to a pivotal role in the signal chain. With only two channels and a simple switching mechanism, the SLO has a surprisingly compact architecture for creating such a rich palette of tones.
The book explains how the amp works, the motivation behind its system design, and the performance of its electronics in the context of a real musical performance.
Richard Kuehnel
is a member of the Circuits and Systems Society of the Institute of Electrical and Electronic Engineers.
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| Mastering Basic Electronics |
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| Preamps and Tone Stacks |
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| Power Amps and Negative Feedback |
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| Power Supplies |
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| DC-Coupled Cathode Followers |
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| Effects Loops |
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| Reverb and Tremolo |
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| Crafting a Complete Architecture |
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| Testing Overdrive Dynamics |
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| Measuring Distortion |
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Introduction
Warning: High Voltage!...1
A High-Gain Rocker...1
Acknowledgements...2
Chapter 1: System Design Concepts
An Introduction to Cascading Gain...6
Basic Architecture...9
Chapter 2: Recovery, Tone, and Power Subsystem
Power Amp...19
Grid Bias Supply...21
Plate and Screen Supplies...23
Ripple Filters...28
Plate Circuit Decoupling...29
Hum Suppression...34
Circa 1987 versus 1959 Ripple Filter Architectures...35
Full Power Performance...36
Long-Tailed-Pair Phase Inverter...39
5F6 Bassman Design...40
SLO Design...43
Global Negative Feedback...46
How Feedback Works...46
How Negative Feedback Reduces Distortion...48
Feedback Calculations for the SLO...49
Presence Control...50
Modified Bassman Tone Stack...52
How the Stack Works...52
SLO versus Tweed Bassman...57
Master Volume Controls...58
Effects Recovery and Tone Stack Driver...59
Headroom...60
Cathode Follower DC Coupling...61
Subsystem Profile...64
Subsystem Interfaces...67
Subsystem Voicing...67
Full Power Performance...68
Overdrive Dynamics...71
Feedback Effects...72
Bias Excursion...72
Power Supply Sag...73
Chapter 3: Effects Driver Module
Partially Bypassed Cathode Resistor...78
Preamp Overdrive...81
Grid-Stopper Resistor...82
Module Frequency Response...84
Effects Pedals...85
Subsystem Input Sensitivity Reference Levels...87
Module Interfaces...88
Chapter 4: Normal Channel Module
DC and AC Conditions...90
Gain and Output Impedance...91
Cascading Gain?...92
Switched Input Network...93
Module Frequency Response...96
Module Interfaces...98
Chapter 5: Overdrive Module
Third Stage...100
Second Stage and Attenuator...103
Input Network...107
Module Voicing...108
Cascading Gain...109
Module Interfaces...110
Chapter 6: Preamp Module
Module Interfaces...115
Chapter 7: Preamp Subsystem Performance
Subsystem Profile...116
Subsystem Voicing...120
Chapter 8: Preamp Overdrie Dynamics
Technology for "Sonic Depth, Clarity, and Dynamics"...123
12AX7 Grid Current...128
Grid Current's Impact on the Effects Driver Module...131
Bias Excursion...135
The Science of Sustain...137
Intermodulation Distortion...142
Upstream and Downstream Voicing...145
A Final Note on Voicing...149
Chapter 9: Optical Switching
VTL5C1 Optocoupler...150
LED DC Conditions: Footswitch Closed...152
LED DC Conditions: Footswitch Open...156
Some Final Words on the Soldano SLO...160
Appendix: Decibel-Volts (dBV)...164
Index...165
